by Kristen Monaco
A growing body of research indicates that obesity is a disorder of the energy homeostasis system, according to a new Endocrine Society scientific statement.
Led by task force chairman Michael Schwartz, MD, of the University of Washington in Seattle, and colleagues, the statement suggested that obesity is caused by two distinct processes: energy homeostasis and energy imbalance -- specifically, energy intake greater than expenditure.
The statement appeared online in the Endocrine Society's journal, Endocrine Reviews.
Energy homeostasis refers to the establishment of a new and higher body weight "set point" matching energy intake and expenditure, referred to as an "upward setting." This mechanism subsequently leads to sustained body weight over time, as well as regaining of weight after diet or lifestyle changes in many cases.
"Because of the body's energy balance adjustments, most individuals who successfully lose weight struggle to maintain weight loss over time," Schwartz stated in a press release. "To effectively treat obesity, we need to better understand the mechanisms that cause this phenomenon, and to devise interventions that specifically address them. Our therapeutic focus has traditionally been on achieving weight reduction. Most patients can do this; what they have the most trouble with is keeping the weight off."
"Healthcare providers and patients need to view this tendency as the body's expected response to weight loss, rather than as a sign of a failed treatment regimen or noncompliance with treatment," he added.
Nearly one-third of U.S. adults struggle with obesity, and effective (especially, cost-effective) treatment options are limited. Therefore, additional research geared towards this specific mechanism of weight gain should be the focus of future obesity research, the authors recommend.
Schwartz and colleagues also explained that obesity differs from other endocrine-related disorders -- many of which already have well-established forms of effective therapy. However, barriers to research on obesity pathogenesis, including time and cost, have prevented researchers from gaining much insight into its details, the group wrote.
Other potential contributing factors for obesity referenced in the statement include genetic predisposition. However, the evidence is mixed on this subject, and studies that have reported a link between genetics and obesity often had very low predictive power. Schwartz and colleagues suggested that future research aim to identify obesity-protective alleles.
"Genetic factors acting in isolation are unlikely to explain the rapid increase of obesity prevalence during the past 40 years," they wrote, noting that the genetic interaction with environmental factors may be a more likely source of increased risk. Environmental interactions, such as exposure to endocrine-disrupting chemicals including PFCs and BPA may play a role increased obesity risk and modifications to insulin sensitivity, the authors noted. Two scientific statements regarding the role of EDCs with obesity risk were previously issued by the Endocrine Society, and the authors recommended future research focus on this risk relationship beyond maternal influences in utero.
Schwartz's group also highlighted the success that bariatric surgery has had as an effective treatment for obesity. They suggested that because such interventions "alter communication between the GI tract and energy homeostasis neurocircuits," as well as microbiome-related changes, these mechanisms may play a significant role in food intake control after surgery, as well as a possible effect on energy homeostasis regulation.
As well, the task force recommended more research on combining neurocognitive and behavioral pharmacotherapy treatments for obesity.
This work was supported by grants from the National Institutes of Health and by the National Institute of Diabetic and Digestive and Kidney Disease–funded Nutrition Obesity Research Center at the University of Washington and the Russell Berrie Foundation.
Schwartz reported relationships with Novo Nordisk. Other authors disclosed several relevant relationships with industry.
